The present invention relates to a copying machine, more particularly, to a copying machine which heats and fuses a toner image by a heating and fusing device after transferring the toner image corresponding to an original image on the copying paper.
The copying machine of a type which forms an electrostatic latent image by scanning and exposing an original, develops the toner image and transfers thereof on the copying paper and fuses the toner image by the heating thereafter has been widely used hitherto.
In the copying machine of such type, speeding of the copying operation has been strongly requested, and recently there are provided a copying machine which has succeeded in equal size copying of the A-4 size original (210 mm.times.297 mm) at 40 sheets per minute or 25 sheets per minute for equal size copying of the A-3 size (297 mm.times.420 mm), which is considered to be a limit for the moving speed of an optical system. In such high speed copying machine, since equal size copying speed of the A-3 size original is 25 sheets per minute, 50 sheets can be copied per minute for reducing it to the A-4 size. Accordingly a capacity large enough to heat and fuse 50 sheets per minute is required as the fusing device, and a large electric current has to be supplied to the heating source in the fusing device. Further, when copying in a reduced size, since the scanning and exposing speed of the original is increased and, normally, the copying papers are fed longitudinally (from in a longer side), the capacity to heat and fuse more than 40 sheets per minute is required as the capacity for the fusing device when changed-over to the lateral feeding (from a shorter side) of the A-4 size, which inevitably needs a larger current to the heating source of the fusing device. However, since the plug socket for the usual home use has a small capacity, there may be a problem that if the required current for the copying machine is large, the use of a copying machine at home in general becomes difficult, or for making it possible to use in the general homes, the electricity to be supplied to the heat source of the fusing device must be suppressed and the copying speed has to be reduced to the copying sheets quantitatively corresponding to the capacity of the fusing device.